1. Field of the Invention
This invention relates generally to high temperature protection tubes, and more particularly concerns a preformed refractory sleeve for a temperature sensing device suitable for repeated immersions into molten metal.
2. Prior Art
As shown by Kraus, U.S. Pat. No. 3,816,183 it is known to surround a support tube and thermocouple unit of a temperature sensing device for repeated immersion into molten metal with a cylindrical sleeve of refractory material. However, due to the cylindrical shape of the sleeve, the relative position of the support tube and therefore the thermocouple unit within the sleeve cannot be controlled with certainty. Therefore, a measuring step is required to control the extent to which thermocouple unit hot junction projects beyond the refractory cement which is applied over the end face of the thermocouple body.